I think that both men and women should have a generous amount of fully paid mat/pat leave in their own right, plus in addition the right to statutory pay. I think employers should offer a "parental" package, rather than a maternity package, so that enhanced pay is offered to any employee having a baby, regardless of sex.
I don't think that we should take from women to give to men.
Men would then, like women, have to consider whether the enhanced package an employer is offering suits their needs when they apply for/accept a job. This may well have the impact of drawing more men into traditionally female roles in the public sector where mat pay tends to be more generous. It will also level the playing field with regard to employers seeing childbearing age women as more of a "risk" than men.
Families would have to make their own decisions as to whether they can afford one parent/both parents/which parent off for whichever length of time suits them up to the maximum 12 months each. Different family situations will mean that different solutions will work for individual families.
In reality, I would think this would mean that men would be more likely to take the first 6/12 weeks off of work, if they were fully paid to do so. This would really help with supporting the mother in the first couple of months after birth, and help with bonding between dads and babies.